Name: People and Place Publisher: Monash University, Centre for Population and Urban
Research Audience: Academic Format: Magazine/Journal Subject: Sociology and social work Copyright: COPYRIGHT 2009 Monash University, Centre for
Population and Urban Research ISSN:1039-4788

Government policy is now very much focused on remedying
isadvantages among Australia's Indigenous population. Consequently
it is important that we have reliable data on the size and
characteristics of this population, especially its age distribution.
This paper analyses statistics on Indigenous birth rates in the Northern
Territory and uncovers some troubling anomalies, to such an extent that
a sceptical observer might wonder if the data might not be in some sense
made up.

INTRODUCTION

Kevin Rudd's commitment to 'closing the gap' between
Indigenous and non-Indigenous standards of living, has highlighted the
paucity of Indigenous population data and a 'frank failure of the
statistical system'. (1) Government priorities reported in the
Australian Government's 2008-09 budget included closing the gaps
for life expectancy, mortality for children under five years old,
literacy and numeracy, employment outcomes, attainment of Year 12
schooling, and access to quality preschool. (2) Each of these indicators
is affected by the Indigenous population's demographic profile, in
particular its age composition.

Understanding Indigenous birth rates is critical in understanding
the demographic profile of the Indigenous population and, consequently,
its relationship with the social-economic world it inhabits. At a more
practical level, birth rates are an essential component of the
population data used in the denominators of the 'closing the
gap' measures. Births data when used for population estimates or
projections are presented as reasonably accurate, and are 'adjusted
slightly for historically observed registration lags'. (3) Data
completeness, or implied coverage, is assessed by comparing the number
of registered births with the number of births estimated from the number
of children enumerated at the most recent census over a five-year
period. This process was first documented by the Australian Bureau of
Statistics (ABS) in Births Australia 1997, (4) but implied coverage was
first reported for South Australia and the Northern Territory in Births
Australia 1993. (5) Indigenous births data are not published if there is
less than 90 per cent implied coverage.

This paper asks whether this assumption of reasonable accuracy is a
valid one to make. Using the Northern Territory (NT) as a case study,
the paper describes where the data used for Indigenous birth rates come
from. It explores what population is being used in order to measure
births and asks whether it is one merely invented by demographers. This
is timely following the recent release of the NT government's
population projections, which show a projected increase in the NT
Indigenous population from 64,006 in 2006 to 81,585 in 2021. (6) The
paper closes by exploring the implications of using current birth rates
for understanding the mechanics of both the size and momentum of
population growth and, also, for understanding Indigenous peoples and
their high-profile disadvantage.

CALCULATING BIRTH RATES

Birth rates are computationally simple to create--the number of
births to women in a defined age group in a given year is divided by the
total mid-year population of women in that defined age group. The
robustness of the rate is affected by the quality of the data used to
calculate it. Well-recognised deficiencies that can affect data quality
include the completeness of birth registration, and accuracy of
characteristics of the births, including geographic location, date, and
demographic characteristics of the mother. (7) The reliability of the
rate is also affected by how well the births truly relate to the
population at risk, essentially whether the births and population data
are for the same group of women. This is a particular problem when
matching vital registration and population data for sub-population
groups based on Indigenous status as has been shown in Australia, (8)
New Zealand (9) and the United States. (10) Matching of the births and
population data is further confounded by the fact that data quality
issues (of completeness and of accuracy of characteristics) can
differentially affect different data sources. Indigenous births and
population data are examined to understand where the data used to
calculate birth rates come from. At issue is whether 'Indigenous
fertility rates' can be viewed as demographic facts, given the data
problems that emerge.

[FIGURE OMITTED]

BIRTHS DATA

Births data for the NT are available from two sources--vital
registrations, from the Registrar of Births, Deaths and Marriages which
are managed by the ABS, and perinatal data, from the Department of
Health and Families' NT Midwives' Data Collection. The NT
Midwives' Collection includes information on all births of at least
20 weeks gestation or 400 grams that take place in the Northern
Territory, and are available by time of the birth. The vital
registrations are for all births registered to mothers who are normally
resident in the Northern Territory, and are available by time of the
birth's registration." One would expect a reasonably close
match between the two datasets given that they both measure the same
outcome, a live birth, albeit in different ways. As Figure 1 shows,
however, the NT Midwives' Collection consistently counts fewer
births each year than do vital registrations. For the period for which
both datasets are available, there are on average 98 more births to
Indigenous mothers registered each year than are recorded in the NT
Midwives' Collection. Choice of dataset alone will therefore
influence the birth rates calculated, with the vital registrations
showing higher fertility levels than the perinatal data. Interestingly,
in most other states and territories perinatal datasets record higher
numbers of births than do vital registrations. (12)

This difference between the two datasets has been reported as
incomplete recording of births in the NT Midwives' Collection in
the past. (13) The different mechanisms of data capture warrant closer
examination to determine if this is actually the case. There are two
issues to be explored: firstly, whether the data collection systems
capture all births and, secondly, whether the data collection systems
record characteristics of the mothers and babies correctly.

The NT Midwives' Collection is a population-based census of
all births that take place in the Northern Territory. Government policy
in the Northern Territory is for all women to birth in hospital, except
for a small homebirth service in Darwin and Alice Springs. For women
living outside one of the four centres with a hospital providing
maternity services (Darwin, Nhulunbuy, Katherine and Alice Springs),
this means transfer into town for 'sit down' at 38 weeks
gestation, or earlier, if the pregnancy is deemed high risk. (14) From
1996, most of the information about births has been captured
electronically. (15) In the public sector, midwives enter data shortly
after the birth of a baby via the hospital information system (CareSys).
Births in the Darwin Private Hospital and planned home births are
entered via the NT Midwives' Collection intranet site. Births in
health centres that do not involve admittance to hospital are submitted
in paper form and entered by the perinatal data manager. (16) Most
Indigenous women birth in one of the Northern Territory's public
hospitals (17) (94 per cent in 2005), thus information about the birth
is automatically captured electronically. (18) Extensive checking of
health clinic records is also done by the perinatal data manager to
ensure data are complete.

It is difficult to imagine that, according to ABS data, up to 200
Indigenous women in a year could be pregnant and give birth without the
woman or her baby coming in contact with the public health care system
at all and thus not have the birth recorded in the perinatal data
collection. This is what is suggested, however, by identifying the
perinatal births as an undercount. While mothers who live remotely may
avoid the health clinics in order to avoid being transferred to town,
(19) the number of identified births taking place in remote communities
is small. (20) A 2007 review of maternity services in the Northern
Territory did find that the various components of maternity services had
different patient information systems, none of which were linked to
provide for data sharing. (21) The review focused on information sharing
of clinical care outcomes (for example, infection rates and adverse
incident rates) and did not identify that different information systems
led to births being excluded from the official counts altogether.

It is possible that this difference in the number of births to
Indigenous mothers is because of different identification of who is
Indigenous. Indigenous status in the vital registrations depends on self
identification, whereas health service providers may assume Indigenous
status (or not) on behalf of women when information is collected for the
NT Midwives' Collection. While different identification of
Indigenous status may affect birth numbers to Indigenous mothers, the
higher number of births recorded via vital registrations are evident for
all births irrespective of Indigenous status. (In 2005, for example,
3659 births were registered to Northern Territory mothers, and 3555
births were recorded as being born to Northern Territory women in the NT
Midwives' Data Collection.)

It is more likely that the systems used affect both the way in
which people are identified as Indigenous and the total number of
births. The NT Midwives' Data Collection is an epidemiological
dataset maintained for the purpose of monitoring pregnancy outcomes and
it is the responsibility of health professionals and health bureaucrats.
Vital registrations, on the other hand, are the means of proving that a
birth has taken place, and provide a child with an official identity
recognised by the state. Registering a birth in the Northern Territory
is a two-fold responsibility. Firstly, the hospital or health clinic
provides a 'Notification of Birth' to the Registrar of Births,
Deaths and Marriages within ten days of a birth taking place. (22)
Secondly, there is a 'Birth Registration Statement', a form
completed for every child by the child's parents, which must be
submitted to the Registrar within 60 days of the birth. (23)

A number of processes surround the collection of vital
registrations that could explain the different birth counts compared to
the perinatal data. The public hospitals in the Northern Territory
provide a weekly notification to the Registrar of births that have taken
place in the previous week. Information is derived from CareSys and
includes information on mother's name, date of birth, place of
usual residence and Indigenous status. This is the same information
system used to inform the NT Midwives' Data Collection.

Mothers are provided with the Birth Registration Statement form
following the birth of their child. This usually takes place in the
hospital before the mother is discharged. Forms are also available at
community health clinics for women who birth in their community. In the
five Northern Territory public hospitals, Aboriginal Health Workers and
Social Workers are available to assist mothers who don't understand
the form. Often these workers will fill the form in on behalf of
mothers, and the mothers then sign it. In the Royal Darwin Hospital
(where the largest number of Indigenous births take place every year),
Aboriginal Liaison Officers (ALOs) help all Indigenous mothers fill in
birth registration forms. ALOs submit registration forms to the
Registrar as well as relevant forms to Centrelink (for Medicare,
parenting payments, and so forth). At the Alice Springs Hospital, a
staff member from the Office of the Registrar of Births, Deaths and
Marriages visits twice a week to collect forms, and help women fill them
in if required. The Aboriginal Liaison Officers in Alice Springs also
work as translators when necessary to help women complete the form.

Once the Birth Registration Statement is received by the Office of
the Registrar of Births, Deaths and Marriages, it is checked against the
Notification of Birth. If there is any difference between the
information about the parents or child from the Notification of Birth
and what is recorded on the Birth Registration Statement, it is the
information on the Birth Registration Statement that is entered into the
vital registrations database (for example, Indigenous status of parent,
place of usual residence, and name).

Incomplete registrations occur when the child has no name, or only
a partially completed Birth Registration Statement is provided. If no
Birth Registration Statement is received within 60 days following the
birth, and the Birth Clerk believes it can be obtained, a variety of
mechanisms are used to find the mother and ensure a form is completed.
If the mother is unable to be found, the birth is registered based on
the information from the Notification of Birth. Statistically, an
incomplete registration is the same as a full registration. If the birth
is registered at a later date, it is linked to the original Notification
of Birth so no duplication occurs. If no Notification of Birth is
received, which is a very rare situation, then the birth cannot be
registered.

Given that the number of births for the NT Midwives' Data
Collection and vital registrations have their genesis in the same
information system (CareSys), the different counts that emerge are
puzzling. One explanation is the use of different names among Indigenous
peoples. Indigenous babies are often given several names and the
possibility of one baby being registered under two different names is
often raised. Staff at the Office of the Registrar of Births, Deaths and
Marriages have said that this is not a problem that they have identified
in matching the Birth Registration Statement with hospital Notification
of Birth information. Furthermore, the processes in place for
registration mean that it is information about the birth such as date,
time and place of birth, birthweight and parents' address, that
allows matching of records to take place, not the baby's name
(Wendy Endenburg and Yvonne Killalea, personal communication). Moreover,
a birth would not be able to be registered if a Notification of Birth
had not been received, and efforts to obtain such a Notification are
likely to identify whether the birth in question has already been
recorded under a different name.

Another explanation for the different birth counts between the two
systems is a different impact of women's interstate travel to give
birth. Both the vital registration and perinatal data systems record
place of usual residence for the mother. 'Place of usual
residence' has been identified as problematic for a mobile
Indigenous population. (24) It is an issue for birth statistics within
the Northern Territory boundary. This is because Alice Springs is an
important service centre with a hospital for communities across the
Australian centre, including communities in South Australia and Western
Australia. (25) Each data system deals with interstate births in
different ways, which could contribute to the different birth counts.

The NT Midwives' Data Collection includes information on all
births that occur in the Northern Territory, and mothers who normally
reside interstate are identified separately. Birth rates, and most other
measures looked at using the dataset, are based on births to Northern
Territory mothers. (26) Similarly, vital registrations are derived from
the Birth Registration Statement, which must be submitted in the state
or territory where the birth takes place. When vital registrations data
are published or purchased based on usual place of residence of mother
(in this case, the Northern Territory) births to mothers who usually
live in the Territory that took place interstate are also included, but
they are not differentially identified. (27) Data from the NT
Midwives' Collection are not available in this way.

Interstate travel to give birth could affect the data in two ways.
Firstly, women who usually live interstate, but birth in the Northern
Territory, could have the birth registered in the NT, particularly if
they have come into town for 'sit down' from a remote
community. Thus vital registrations could be high because they include
NT usual residents who birth in the NT and interstate residents who
birth in the NT. While it is not unreasonable to assume some interstate
women might be recorded as being NT residents, it seems unlikely that
usual place of residence for interstate women would be consistently
identified correctly in the Midwives' Collection, but not for
births' registrations data. A second effect of interstate travel is
that the difference between the two datasets could reflect NT women
giving birth interstate, the numbers for which are able to be captured
by vital registrations but not the Midwives' Collection. The AIHW
National Perinatal Statistics Unit published information on interstate
births for the first time in a report of 2004 data, but not
disaggregated by Indigenous status. (28) In 2004, 138 NT women
(Indigenous and non-Indigenous) gave birth interstate, yet the
difference in Indigenous birth counts between the two data collection
systems in that year was 151. Anecdotally, it is well known that many of
these interstate births are military wives/partners who travel home to
give birth if their husband/partner is posted overseas at the time of
the birth.

Alice Springs Hospital is the place where state-based confusion
about place of usual residence would be most likely to occur because of
its proximity to state boundaries. A 2008 audit of patient demographic
data at NT hospitals found that miscoding of usual state of residence
was only found for patients incorrectly identified as usually living in
Alice Springs Urban or Alice Springs Rural health districts. (29) If the
difference in counts between the vital registration and perinatal
datasets is because of different counts of interstate births (both in
and out of the collections), then it is likely to be concentrated around
Alice Springs. This would mean that some of those births recorded to
mothers in the Alice Springs Urban and Alice Springs Rural health
districts were actually births to interstate mothers. This would have
the effect of suppressing the number of births in the NT Midwives'
Data Collection even further, thereby exaggerating the difference with
the vital registrations data.

A perfect match between the datasets is unlikely because of the way
births are reported--by year of occurrence in the NT Midwives' Data
Collection and by year of registration for the vital registrations. In
the Northern Territory, most births to Indigenous mothers are registered
within three months of occurrence, and delays in registration in one
year should be balanced by delays from other years. In 2005 and 2006,
only 0.3 per cent of births registered to Indigenous mothers usually
resident in the Northern Territory were for births that occurred over a
year prior to registration. (30) While a perfect match may be unlikely,
this relatively quick registration from time of birth indicates that any
differences between vital registrations and the perinatal data should be
fairly small, but this is clearly not the case.

There is no clear resolution to the question of which dataset is
more accurate without much more detailed investigation of both datasets,
a matching of records and closer observation of the data collection,
data entry and data cleaning processes. More information about
interstate births to Indigenous mothers is also needed. Two
possibilities remain to explain the different counts--the NT
Midwives' Data Collection is missing births, or the vital
registrations are counting some births twice. Staff responsible for the
respective datasets cannot identify any areas where this might occur.
Laws et al. (31) view the perinatal data as more accurate than vital
registrations, and the NT Government has based its population
projections on fertility levels from the NT Midwives' Data
Collection. (32) But at a national level, it is vital registrations that
are used for population estimates and projections. (33) Vital
registrations are also available in a much more timely fashion. (In the
Northern Territory, 2003 to 2005 perinatal data became available in
2009, whereas vital registrations were available for 2007 in October
2008.) In the absence of clear proof one way or the other about which
dataset is more accurate, users of either dataset must be clear that
their choice of dataset will result in different social facts, namely a
higher or lower fertility rate. At a macro level this has implications
for predicted population age structures and intergenerational transfers
of knowledge and wealth, and at a micro level it can affect planning
decisions for fundamentals such as how many houses should be built, how
many teachers need to be employed, and how many hospital beds will be
needed.

THE DENOMINATOR

Birth rates are not based on births data alone. Births must be
related to a population. In Australia, population data are derived from
the five-yearly census, with counts of the Indigenous population
available from 1961 (although official counts were not published until
1971). (34) A characteristic of Indigenous census counts is the increase
in counts from census to census beyond the growth that would be expected
from births and deaths alone. An analysis of the increase from 1991 to
1996 concluded that the balance between the explainable increase and the
census counts was affected by different undercounts of the Indigenous
population at each census, changes in non-response to the Indigenous
status question, and changes in the way Indigenous people answer the
Indigenous status question. (35) The birth of Indigenous babies to
non-Indigenous women is also a contributing factor. (36) This issue of
who is counted adds a temporal component to the data that undoubtedly
reflects social change in attitudes (both towards Indigenous people, and
among Indigenous people themselves), and gives rise to complex reasons
why population measures based on these data may change.

While there is a well-documented phenomenon of increased Indigenous
counts from census to census, the key issue is that of undercounts.
Since 1986, the ABS has had an Indigenous Enumeration Strategy (IES),
the aim of which is to improve the enumeration of Indigenous people.
Detailed observations of the IES implementation in the Northern
Territory for the 2001 and 2006 censuses show that, despite increasing
attention and funding to ensure people are counted, many Indigenous
people remain excluded from the census count. (37) Taylor and Biddle
concluded that: 'in many parts of Australia ... undercounting of
the Indigenous population in 2006 has reduced the census to the role of
a large sample survey'. (38)

In 2006, for the first time, the Post-Enumeration Survey (PES),
carried out one month after census night and used to determine how many
people were missed in the census, included remote areas of Australia and
discrete Aboriginal communities. It showed that across Australia the
Indigenous population had been undercounted by 11.5 per cent. In the
Northern Territory this undercount was 19.2 per cent. (39)

In response to this undercount, the ABS creates an Estimated
Resident Population (ERP). In addition to the undercount, the ERP takes
account of individuals for whom Indigenous status is not known. These
individuals include those not counted at all, and individuals who were
counted but for whom Indigenous status was not collected.

While technically, the 2006 ERP is, 'probably the best
estimate yet of the nation's Indigenous population', (40) its
calculation is not straightforward. It requires, 'constructing an
'Indigenous population' ... out of 'Indigenous
peoples'. (41) This population construction has led to an NT
Indigenous ERP that is 24.1 per cent larger than the population counted
by the census. (42) It may be overstating the case to claim the
Indigenous population is 'made up', but there are data and
methodological assumptions used to determine the final ERP that, if
changed, could lead to a different outcome.

If the 2006 ERP is Australia's 'best estimate yet'
of the Indigenous population, then it raises concerns about what
population is used to look at changes over time. The ABS does not
attempt to make Indigenous ERPs based on different censuses consistent.
Rather, it produces a new ERP, creating a backcast (usually no greater
than 10 years) based on an assumption of natural increase. Wilson and
Barnes have shown how these backcast Indigenous populations have been
higher than census year Indigenous ERPs in every state across Australia.
(43) The creation of backcast Indigenous populations for the NT based on
the 2006 ERP show larger Indigenous populations than counted in all
censuses prior to 2006. As the NT Department of Health and Families has
shown, a larger backcast population demonstrates the need to reassess
all historical rates created using census-based population denominators.
(44)

This creation of an Indigenous population across time, to
increasingly higher levels, while methodologically sound (45) and
undoubtedly reflective of reality, (46) has important implications for
how we understand birth rates. Figure 2 shows teenage fertility rates
calculated in three ways: rates published in the ABS annual Births
Australia publications, based on ERPs for the year of publication; rates
based on vital registrations using a backcast population denominator;
and rates based on perinatal data using a backcast population
denominator. In addition to the fertility rates being exceptionally
high, (47) four things stand out: each of the datasets produce the same
general pattern of fertility change, namely overall decline with
fluctuations; the higher birth counts for vital registrations than
perinatal data are not evident in every year for this age group;
published rates are consistently higher than those calculated using a
backcast population; and the further back in time the comparison, the
greater the difference.

[FIGURE OMITTED]

The demographer's access to clean data to create populations
for analysis gives him or her the power to influence political
decision-making, social commentary and even to determine history. Gray
referred to this relationship as 'political demography' (48)
and Taylor has claimed the relationship 'is strong and has never
been stronger'. (49) This 'political demography' becomes
embedded as the trends shown by Indigenous birth rates, particularly the
rate of change, are influences that shape the very assumptions about
what will happen to birth rates into the future. It is these assumptions
that then are used in future population estimates and projections.

CONCLUSIONS

This paper asks whether we are just making up Indigenous birth
rates. It has demonstrated that birth rates are based on some best ever
estimates in the case of population denominator data, and seemingly
rigourous (if different) counting processes in the case of births. While
Indigenous birth rates are not made up, in the sense of being invented,
they are based on data that cannot be taken at face value and they must
be viewed as indicative, rather than precise.

Herein lies a significant problem. Despite evidence of Indigenous
population data being undercounted and imprecise, population measures
based on Indigenous status continue to feed into government policy
settings and programs, and into wider societal views of Indigenous
peoples, without caveats on data quality. There is a very real risk that
the Kelvin dictum is applied to mean: 'if you can't measure,
measure anyway'. (50) Nowhere is this more evident than in the use
of birth rates for population projections. The Northern Territory
population projections released in 2009 are based on a total fertility
rate (TFR) calculated from the NT Midwives' Data Collection that is
the average over the period 2001 to 2005, using an ERP derived from the
2001 census. The TFR is thus lower than what would be expected if a TFR
based on the vital registrations were used (2.37 birth per woman
compared to 2.90 births per woman), which obviously affects population
size into the future. Using a basic projection model assuming zero
migration, these different TFRs show the Indigenous population growing
from 64,000 to 101,000 and 113,000 respectively over 30 years. The
difference of 12,000 people is larger than every town in the Northern
Territory except Darwin and Alice Springs. The 2001 to 2005 ERPs used in
the 2009 NT projections are also smaller than populations backcast from
the 2006 ERP. Thus the TFR used in these projections is slightly higher
than the one calculated from a 2006-based population (2.37 births per
woman compared to 2.26 births per woman). ATFR of 2.26 leads to a
projected Indigenous population of 98,000 over 30 years. Not only do
different TFRs lead to different projected population sizes, they also
lead to different population age structures.

The point, however, is not to quibble about how accurate the
projections are. (51) The point is that once entered into the public
arena the projections become powerful numbers and are inherently
political. The population projections give us our macro-level framework
for understanding current and future disadvantage as influenced by age
structure, cohort size and intergenerational period. Similarly, backcast
populations can cause us to revise history.

Acknowledgements

This research is supported by an ANU PhD Scholarship, the
Australian Population Association's Alan Gray Grant and J.C.
Caldwell Grant. Thank you to Tom Wilson for his help establishing the
impact of different fertility rates on population projections. Comments
from Rebecca Kippen, Elizabeth Creed, Elizabeth Ganter, Bob Birrell and
an anonymous reviewer on earlier drafts of this paper are gratefully
acknowledged. Any contestable claims or errors are my own.

(11) Birth registration data are available by time of birth if
requested from the ABS, however, they are generally not released for
more recent years when data are deemed incomplete because of late
registrations. Annual publications of birth registrations are for births
registered in the reference year of the publication.

(17) There are five public hospitals in the Northern Territory,
including the four that provide maternity services and Tennant Creek
Hospital where some women give birth if they go into labour and are
unable to be transferred to Alice Springs. There is also one private
hospital in Darwin.

(18) Zhang and Johnstone, 2009, op. cit.

(19)S. Ireland, 'Niyith Niyith: The Quiet Story--Exploring the
experiences of Aboriginal women who give birth in a remote community in
the Northern Territory', unpublished thesis, Degree of Bachelor of
Science with Honours, Graduate School of Health Practice, Charles Darwin
University, 2009; S. Kildea, And the women said ... Reporting on
Birthing Services for Aboriginal Women from Remote Top End Communities,
Darwin, Territory Health Services, 1999

(20)Zhang and Johnstone, 2005, op. cit.

(21)Banscott Health Consulting, 2007, op. cit.

(22) Homebirth midwives must also report births which they are
present for to the Registrar of Births, Deaths and Marriages.

(25) J. Taylor, The Spatial Context of Indigenous Service Delivery,
CAEPR, The Australian National University, Canberra, 2002

(26) Zhang and Johnstone, 2005, op. cit.

(27) A summary table of state or territory of usual residence of
mother and state or territory of registration is included in the annual
Births Australia publications produced by the ABS, but the information
is not disaggregated by Indigenous status. In 2005, for example, 92
women from interstate registered a birth in the NT and 106 NT women
registered a birth elsewhere.

(50) Lord Kelvin is quoted as saying: 'I often say mat when
you can measure what you are speaking about, and express it in numbers,
you know something about it; but when you cannot express it in numbers,
your knowledge is of a meagre and unsatisfactory kind: it may be the
beginning of knowledge, but you have scarcely, in your thoughts,
advanced to the stage of science, whatever the matter may be'. From
'Electrical units of measurement', a lecture delivered at the
Institution of Civil Engineers, London (3 May 1883), Popular Lectures
and Addresses (1889), vol. 1, no. 73. From

(51) As the Northern Territory Treasury quite rightly point
out:' ... the population projections should not be interpreted as
accurate forecasts or predictions. They are the result of applying
certain assumptions about the future direction and levels of fertility,
mortality and migration, to a base population'. Northern Territory
Treasury, 2009, op. cit.